Changes in the distribution of HIV type 1 subtypes D and A in Rakai District, Uganda between 1994 and 2002

Abstract

HIV-1 subtype D (HIV-1D) progresses to disease faster and has lower transmissibility than subtype A (HIV-1A). We examined whether these differences could lead to a population level change in the distribution of these subtypes over time. HIV-1 viral RNA was extracted from stored serum samples from HIV-positive subjects participating in a population-based cohort study in Rakai, Uganda in 1994 and 2002. Portions of the viral proteins gag and gp41 were sequenced and subtyped. HIV-1 subtype assignments were generated for 773 subjects in 1994 and 812 subjects in 2002. The change in subtype distribution of the population as a whole as well as quartile age groups were examined for significant changes using a linear model. There was a significant decrease in the proportion of subjects infected with HIV-1D from 70.2% to 62.4% and a significant increase in subjects infected with HIV-1A from 16.7% to 23.3% over the 8-year period (p = 0.005). The most marked changes in proportion of HIV-1D and A were seen in the younger individuals (<25 and 25-30 years; p < 0.05). The percentages of subjects infected with HIV-1C and recombinant subtypes did not change significantly. Over this 8-year period, the overall viral population in this region evolved toward the less virulent HIV-1A strain, most likely as a consequence of the faster disease progression and lower transmissibility of HIV-1D.

FIG. 1.

The trial profile of the subject population from which sequence data were obtained is shown for 1994 and 2002.

FIG. 2.

The amount of change from 1994 to 2002 in the proportion of HIV-1A and D is shown for the four age groups examined. The linear model's 95% confidence intervals are shown with significance indicated (*p < 0.05). The model fitness was examined based on the significance of the residuals. (Color image can be found at www.liebertonline.com/aid).